(1) Field of the Invention
The invention relates to a method of barrier layer formation in the fabrication of integrated circuits, and more particularly, to a method of forming a CVD molybdenum nitride barrier layer to prevent copper diffusion in the manufacture of integrated circuits.
(2) Description of the Prior Art
In a common application for integrated circuit fabrication, a contact/via opening is etched through an insulating layer to an underlying conductive area to which electrical contact is to be made. A barrier layer, typically titanium nitride, is formed within the contact/via opening. A conducting layer material, typically tungsten, is deposited within the contact/via opening. As device sizes continue to shrink, these typical materials are no longer adequate. Because of its lower bulk resistivity, Copper (Cu) metallization is the future technology for feature sizes of 0.18 microns and below. Cu metallization requires a good diffusion barrier to prevent the copper from diffusing through the active junctions. The inventors have found that Molybdenum nitride (MoN) is a good diffusion barrier for Cu.
U.S. Pat. No. 5,646,426 to Cockrum et al discloses a MoN film deposited by reactive sputtering under Indium. U.S. Pat. No. 4,960,732 to Dixit et al teaches a barrier layer of MoN for use with a tungsten plug. U.S. Pat. No. 4,431,708 to Carver et al teaches forming a molybdenum film and annealing it to reduce resistivity. None of the references disclose CVD MoN as a diffusion barrier for Cu.